Here are some things to look for before your next purchase

Buying a Mower is a big investment and a big decision, one that requires a fair amount of discussion and research on the front end. After the purchase has been made, these same operators will look to follow a routine maintenance schedule to protect their investment.
You should look for a dealer that will be there for the customer: on the front end, during the buying process, and afterwards by providing parts and service support.
Look to your dealer to be more than a salesperson. A good dealer will ask questions to determine the makeup of the properties you maintain, and to better understand how you plan to use your new mower.
Then that dealer should give you plenty of opportunity to try out the mower, generally at a planned demonstration at a site of your choosing..
Spend as much time as you need during a demonstration to get a good "feel" for the mower. If you need more time, ask your dealer. They should take every step nessasary to ensure that you're as comfortable as you need to be before making a purchase.
Service support
Before buying a Mower, make sure up front that the dealer stocks a good supply of both fast-moving and slower-moving parts, and that the technicians are trained to work on the mowers and can perform all functions.
Look around the shop and ask to see the parts room. Talk with the technicians and then talk with other landscapers in the area to find out how your dealer stacks up.
Then ask your dealer about repair times. For commercial operators, time is money and down time is lost money. Your dealer should strive to offer a 24-hour turnaround on repairs, or be in a position to offer a loaner if a machine can't be fixed in that time frame. Ask them if they offer priority air freight to help keep your equipment up and running.
Non-equipment service
Service is more than fixing equipment on a timely basis. The most successful dealers work closely with the customer, from the point of sale and demonstration process to providing exemplary after-sale service.
Some dealers are in a position to help their customers with non-equipment issues. They might even be able to give advice about operating a business, including job costing, estimating, employee relations, insurance and margins. Some may even offer formal seminars on business topics and service seminars.
Other dealers make a point to offer daily maintenance training for operators.
The most successful dealers are those who work closely with the customer from the point of sale and the demonstration process to providing exemplary after-sale service. This is the value they offer customers and this is what separates them from cost-cutters, mass merchants, big box stores and others that don't offer service.
In many ways, your dealer will resemble the products he sells. If he sells quality products that require quality service, expect him to be in a position to deliver. But like the products he sells, price is only a beginning point of discussion -- the end point is how that dealer and product will deliver for you.

these things are all important and another simple way to know if your going to get good service is to see if they post some sort of guaranty at the dealership and that it is not just a sales speach that it will be backed up, a way you could know is to be comfortable with numbers if you see multiple unit or if they sell alot, there knowledge and parts availablity on that model will be good.